Hi Bill,
Sorry, forgot to answer your other question. These have been in service since the weekend and have been experiencing problems since then.
Before there was a mixture of x460 and 400's, but none of them stacked. Was running a mixture of Extremeware and EXOS, but as I said, no stacking.
From a logical level the design now looks like a single link end to end using stacking and lags, so there is no spanning tree configured.
Many thanks,
Martin